Apparatus for tripping a system for the protection of occupants of a vehicle

ABSTRACT

An apparatus for tripping a system for the protection of occupants of a vehicle has a first sensor (10) for sensing the acceleration of the vehicle in its direction of forward motion and a second sensor (12) for sensing the acceleration of the vehicle in a direction transverse to its direction of forward motion. The two sensors are under the control of control devices (14,16) which trigger the occupant protection system in dependence upon the signals from the first and second sensors (10,12).

STATE OF THE ART

The present invention relates to an apparatus and method for actuating asafety system for a motor vehicle based upon the signals generated by anacceleration sensor.

In known vehicle occupant restraining devices, such as inflatableairbags, the devices are actuated when the acceleration of the vehicle,as measured by an accelerometer, is above a certain value whichindicates that the vehicle has crashed. However, the known sensorsystems often actuate the restraining devices too late if the impact isoblique (e.g. 30°) or if the impact is a slow offset crash. This is due,mainly to the greatly differing energy-absorption behavior of vehicleshaving a crumple zone in the case of frontal and oblique impacts.

Known systems for determining the acceleration of the vehicle are eitherin the form of a central sensor system or in the form of a plurality ofdecentralized sensors. However, in both cases, the acceleration signalis measured only in the longitudinal direction of motion of the vehicle,resulting in problems in actuating the occupant restraining device whena significant acceleration is experienced along an axis other than thelongitudinal direction of motion of the vehicle.

In U.S. Pat. No. 3,851,305 (column 8, lines 14-23) an electric collisiondetecting system is described wherein a collision detector is providedfor producing a collision signal when an object contacts the motorvehicle, and wherein a deceleration dectector is provided for producinga real deceleration signal. Both detector types are arranged apart fromeach other in the front part of the vehicle.

It is an object of the present invention to provide an apparatus andmethod of triggering vehicle occupant restraining devices which will beeffective in actuating the devices even if an impact on the vehicle isnot a frontal impact.

DRAWINGS

By way of example only, specific embodiments of the present inventionwill now be described, with reference to the accompanying drawings, inwhich:

FIG. 1 is a diagrammatic representation of a first embodiment of atriggering apparatus for an inflatable airbag, in accordance with thepresent invention;

FIG. 2 is a diagrammatic representation of a second embodiment of atriggering apparatus for an inflatable airbag in accordance with thepresent invention;

FIG. 3 is a diagrammatic representation of a third embodiment of atriggering apparatus for an inflatable airbag, in accordance with thepresent invention; and

FIG. 4 is a diagrammatic representation of a fourth embodiment of atriggering apparatus for an inflatable airbag, in accordance with thepresent invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring firstly to the first embodiment, illustrated in FIG. 1, theapparatus comprises a sensor 10 for detecting the acceleration of avehicle along an axis parallel to the forward direction of motion of thevehicle (hereinafter referred to as the longitudinal direction), and asensor 12 for detecting the acceleration of the vehicle along an axisinclined at right angles to the longitudinal axis (hereinafter referredto as the transverse direction). The longitudinal acceleration sensor 10and the transverse acceleration sensor 12 feed signals a_(x) and a_(y)to respective evaluation devices 14, 16. The evaluation devices 14, 16may, for example, be in the form of electronic integrators.

If the evaluation means 14 determines that the longitudinal accelerationis greater than a predetermined threshold value then the evaluationmeans 14 sends a signal b to an output stage 18 which is in the form ofa transistor switch. The output stage 18 is effectively an electrical orelectronic switch actuated by the signal b, and sends a further signal cwhich actuates actuation capsules 20, the present example being for thecase of an inflatable restraining bag.

It will be noted from FIG. 1 that the output of the evaluation means 16relating to the transverse acceleration is fed into the evaluation means14 relating to the longitudinal acceleration. The signal from theevaluation means 16 relating to the transverse acceleration is used tochange the evaluation algorithm of the evaluation means 14 relating tothe longitudinal acceleration. In this way , even if the longitudinalacceleration sensed is not above the threshold value for actuating theactuation capsules 20, the evaluation means 14 may determine, uponreceipt of the signal from the evaluation means 16, that the overallacceleration of the vehicle is sufficient for the actuation capsule 20to be actuated, even though neither of the longitudinal and transverseaccelerations would, by themselves, be sufficient to do so. It is alsouseful when, because of the nature of the impact of the vehicle, such asan oblique impact, the eventual acceleration would be sufficient in onedirection for the actuation capsules 20 to be actuated, but only after adelay. The present invention reduces the said delay considerably.

The second embodiment, illustrated in FIG. 2, has the same components asthe first embodiment, illustrated in FIG. 1. However, the signal a_(x)from the longitudinal acceleration sensor 10 is also sent to thetransverse evaluation means 16, in addition to the longitudinalevaluation means 14.

As before, the longitudinal acceleration still forms the basis ofcalculating whether the actuation capsules 20 are to be actuated.However, the two signals a_(x) and a_(y) from the longitudinal andtransverse acceleration sensors 10, 12 are processed together in thetransverse evaluation means 16. In this way, the overall magnitude anddirection of the acceleration of the vehicle can be determined, and theoutput of the evaluation means 16 can be used to change the actuationparameters of the longitudinal evaluation means 14. For example, even ifthe longitudinal acceleration a_(x) is not sufficient for the evaluationmeans 14 to actuate the actuation capsules 20, then, depending on thesignal from the evaluation means 16, the evaluation means 14 may stillsend a signal b to the output stage 18, which in turn actuates theactuation capsules 20 by virtue of a signal c.

The second embodiment thus permits actuation of the actuation capsules20 in certain predetermined conditions.

The third embodiment, illustrated in FIG. 3, is provided withlongitudinal and transverse acceleration sensors 10, 12. Two evaluationchannels, channel 1 and channel 2, are provided, and the outputs a_(x),a_(y) from the sensors 10, 12 are fed into each of the evaluationchannels 1 and 2. The channels 1 and 2 may comprise, for example,components 14 and 16 of FIG. 1 or FIG. 2, and operate in the same way asdescribed in the first and second embodiments respectively, describedabove. Each channel 1 and 2 can then determine, independently of theother channel, whether the components of the acceleration of the vehiclereach the predetermined threshold values, and in the case of a positiveresponse, each channel outputs a signal d. The output from channel 1 isfed into a test switch 22, whereas the output of channel 2 is fed intoan output stage 18', which has a similar function to the output stage 18of the first and second embodiments, but which has four outputs forproviding an actuating signal c to each of four actuation capsules 20,illustrated schematically. The test switch 22 is a further output stage,and in this particular embodiment is identical to output stage 18', orany other transistor switch. The actuation capsules are connectedbetween the output stage 18' and the test switch 22. This arrangementmeans that the actuation capsules 20 may only be actuated if a signal isreceived from both of the channels, 1 and 2. This guards againstpossible mis-evaluation in one of the channels, since the capsules areactuated only if both channels determine that the conditions ofacceleration for actuation of the capsules have been met.

The fourth embodiment, illustrated in FIG. 4, also has longitudinal andtransverse acceleration sensors 10, 12. The acceleration signals a_(x)and a_(y) are fed to respective integrators 24, 26. The integratedsignal from a_(x) is then fed directly to evaluation means 28 whichdetermines whether the signal from the integrator 24 is above thepredetermined threshold value. If this is indeed the case, i.e. that thelongitudinal acceleration is such that the restraining means should beused, the evaluation means 28 feeds a signal b to an output stage 30,which in turn feeds an actuating signal c to the (or each) actuationcapsule 20.

The integrated signals from the integrators 24, 26 are also fed to asecond evaluation means 32. Depending upon the relative magnitudes ofthe two signals a_(x) and a_(y), the magnitude and the direction of theacceleration of the vehicle can be determined, and if they are such asto exceed the predetermined threshold values of the second evaluationmeans 32 (i.e. they are of such relative strengths that an impact whichrequires actuation of the safety means has occurred) a signal A isoutput, and fed into the first evaluation means 28, which, aspreviously, acts to actuate the actuation capsules 20.

The output signals of the integrators 24, 26 are also each fed to afurther respective integrator 34, 36, and the output of the furtherintegrators 34, 36 are fed into a third evaluation means 38. If therelative values of the two doubly-integrated signals exceed thepredetermined values (which indicates that an impact requiring theactuation of the restraining device required) then a signal B is outputfrom the evaluation means 38 and input into the first evaluation means28. The first evaluation means 28 then acts to actuate the actuationcapsules 20.

Thus, the fourth embodiment can act to actuate the actuation capsules 20where the longitudinal acceleration by itself would not be sufficient totrip the actuation, but where the overall acceleration requires thattripping should occur. It is also most beneficial in the case where thelongitudinal acceleration would eventually be sufficient to trip theactuation capsules 20, but only after a delay. This embodiment oftenallows earlier tripping of the actuation capsules, especially where anoblique impact is involved.

The present invention has the advantage that, compared withdecentralized sensors, the arrangement of the sensors in a centralizedunit results in lower installation costs and less risk caused by damageto cable strands. The present invention is also particularly suitablefor adapting existing vehicles, as opposed to fitting the system in anew vehicle, during construction.

The present invention has been described mainly with reference toactuation of an air bag, but it should be appreciated that it canequally well be applied to other safety systems. For example, thesignals b or c from the output stages may be used to tighten safetybelts and/or actuate a central door locking system and/or actuate aflashing warning light system.

The present invention also has the advantage that separate additionalfunctions can be controlled by all round detection of acceleration. Forexample, central locking and flashing warning systems might have allround sensitivity, i.e. may be actuated when the acceleration in anydirection exceeds a predetermined value, an airbag might only beactivated in the case of the frontal acceleration component reaching athreshold value, whereas belt tightness and central belt locking mightbe activated in an all round sensitive manner, depending on the wishesof the vehicle owner.

The second sensor need not detect acceleration in the transversedirection, but may, for example, detect acceleration in a directionother than at right angles to the direction of forward motion. Forexample, the sensor 12 may be adapted to detect acceleration in adirection of oblique impact, e.g. 30 degrees to the direction of forwardmotion.

We claim:
 1. An apparatus for restraining a vehicle occupant during acrash of the vehicle comprising:first crash sensor means securable tothe vehicle and having a sensitivity axis parallel with a front-to-rearaxis of the vehicle for providing a signal having a value functionallyrelated to crash energy directed parallel to the front-to-rear axis ofthe vehicle and substantially impervious to crash energy directedparallel to a side-to-side axis of the vehicle; second crash sensormeans securable to the vehicle and having a sensitivity axis parallelwith the side-to-side axis of the vehicle for providing a signal havinga value functionally related to crash energy directed parallel to theside-to-side axis of the vehicle and substantially impervious to crashenergy directed parallel to the front-to-rear axis of the vehicle, saidfirst crash sensor means and said second crash sensor means having theirsensitivity axes oriented along mutually orthogonal axes; control meanselectrically connected to said first crash sensor means and to saidsecond crash sensor means for determining a direction of a crashcondition in response to the Signals from said first crash sensor meansand said second crash sensor means; and a plurality of actuatableoccupant restraint devices, each electrically connected to said controlmeans, said control means controlling which of said plurality ofactuatable occupant restraint devices is or are actuated in response tothe determined crash direction.